1. Field of the Invention
The present invention relates to apparatus for moving a plurality of pallets loaded with building blocks and more particularly to such apparatus which includes a plurality of horizontal spades adapted for vertical, lateral and rotational shifting of a corresponding plurality of loaded pallets and having an improved rotation mechanism.
2. Description of the Related Art
In automated brick or block making plants, a block machine presses moldable product into a block mold to produce green or uncured blocks. The green blocks are transported to kilns for curing and are thereafter palletized for shipment from the plant.
Usually the block molding machine dispenses a plurality of green blocks on a rectangular metal pallet. The pallets are transported by conveyor to a stacker tower which receives the pallets, one at a time. After a pallet is received by the stacker at the level of the conveyor, the stacker shifts the pallet upwardly and then receives another pallet loaded with block directly therebeneath. This process continues until a vertical stack of pallets, typically about 8-10 in number, are held by the stacker.
The stacker is positioned adjacent a device known as a loader. The loader comprises a vertically-shiftable spade assembly from which a plurality of spades, positioned one above the other, extend laterally. There are the same number of spades in the loader as pallets with the spades being spaced apart from one another the same distance as the pallets in the stacker.
The spades are mounted on a vertical post which extends downwardly from a carriage that is laterally moveable along an axis toward and away from the stacker. The post is connected to the carriage via a ball bearing having a diameter in excess of one foot. An hydraulic rotary actuator mounted on the carriage pivots the spade assembly about a vertical axis. A pair of hydraulic rams are mounted on the spade assembly for vertically shifting the spade assembly in a manner which causes the spades to shift in tandem either upwardly or downwardly.
In operation, when the stacker is filled with loaded pallets, the loader carriage drives the spade assembly toward the stacker until each spade is received just beneath a corresponding pallet. One of the rams on the spade assembly actuates to shift the spades upwardly thereby lifting the pallets. The carriage then withdraws from the stacker, rotates 180.degree. and advances toward a rack positioned at the other end of the spade assembly travel path. The carriage moves the spade assembly bearing the loaded pallets into the rack and a ram on the spade assembly actuates thereby lowering the assembly and depositing the stacked pallets on the rack.
Thereafter, either by way of a forklift or on automated transport cars, the racks are moved into kilns for curing.
After the blocks are cured, the racks are removed from the kilns and transported to a second stacker and unloader which operate in reverse fashion from the stacker and loader as described above and are referred to as an unloader and unstacker. The unloader carriage moves toward the rack bearing the cured block and positions a spade under each pallet. The ram on the spade assembly actuates thereby raising the spade assembly and the corresponding pallets which are then transported laterally by the unloader carriage toward the unstacker. Prior to reaching the unstacker the spade assembly rotates 180.degree. and thereafter drives into the unstacker and deposits the pallets thereon. The unstacker lowers each pallet, one at a time, onto a conveyor which transports the cured block to a palletizing station prior to shipment.
The prior art loader and unloader suffer from several disadvantages which will be described with reference only to the loader because, as set forth above, the loader and unloader are structurally identical but differ in the manner in which each is operated. The large ball bearing in the prior art unloader absorbs the entire load of the spade assembly and blocks supported thereon. This imparts a substantial amount of wear to the ball bearing which must be replaced on a periodic basis. Replacement is both expensive and cumbersome because the entire spade assembly must be removed to replace the ball bearing. In addition, the ball bearing does not provide a stable suspension for resisting wobbling of the spade assembly as the carriage starts and stops.